Process for manufacturing a drive plate

ABSTRACT

In a die forging process, projections (4a) are formed on an inner circumference thereof. The projections (4a) are inserted into holes (46) provided in a disc plate (45). The projections (4a) are crushed by a punch 49 so that the disc plate (45) is securely fixed on an inner circumference of the annular gear 41. The process can eliminate a cutting and an electric welding to shorten a manufacturing time.

FIELD OF INVENTION

This invention relates to a process for manufacturing a drive platehaving a plate integrally secured on an inner circumference thereof.

BACKGROUND ART

A drive plate meshes with a pinion gear securely set on a rotary shaftof a starter motor to start an internal combustion engine.

A conventional process for manufacturing a drive plate is as follows:

A flat bar material is curled, both of its ends are subjected to a flashbutt welding, and its interior and exterior surfaces and its bothsurfaces are cut with a single purpose machine and a lathe tomanufacture an annular gear blank. The annular gear blank is subjectedto a gear cutting with a hobbing machine then a chamfering tomanufacture an annular gear. A plate is pressed on an innercircumference of the annular gear. Electric weldings are performed onten to twelve portions of the plate, each portion having approximately15-25 mm to manufacture a drive plate.

According to such a manufacturing process, a series of processes formanufacturing an annular gear from a flat bar comprise a cutting, a gearcutting, a chamfering, and electric welding, which result in a longmanufacturing time. Thus, an object of the present invention is toprovide a process for manufacturing a drive plate, which processeliminates a cutting and a chamfering process to shorten a manufacturingtime.

Another object of the present invention is to provide a process formanufacturing a drive plate, which process can reduce frictionalresistance between a female die and a workpiece to elongate a usefullife of a die.

A further object of the present invention is to provide a process formanufacturing a drive plate, which process can securely connect a plateto an annular gear.

SUMMARY

According to a process for manufacturing a drive plate of the presentinvention, a die forging process employs a female die having a chamferof 20°-50° on an inlet inner circumference thereof and a fine polishedtooth profile sliding on an annular workpiece. Thus, friction resistancebetween the female die and the annular workpiece at the inlet is reducedand an arc-shaped surface is formed at the ends of tooth profiles of theannular workpiece. After the trimming operation, multiple projectionsformed on an inner circumference of the annular workpiece of the femaledie are inserted into caulking holes provided in a disc plate and thedisc plate is securely provided on the inner circumference of theannular workpiece. The projections are pressed by a punch, so that adrive plate is manufactured, the drive plate having the disc platesecurely provided in the annular gear.

According to the process for manufacturing a drive plate, a pressworking can be performed to manufacture a drive plate without a cuttingand an electric welding, which contributes to a cost reduction. Further,the manufacturing process employs the female die having the finepolished tooth profiles with the chamfers of 20-1500 provided at theinlet of the female die. Therefore, a frictional resistance between thefemale die and the annular workpiece is reduced, so that the useful spanof life a die set, such as the female die, extends, which leads toreduction of a manufacturing cost.

Further, according to the process for manufacturing the drive plate, thedie forging press consists of two processes and the chamfer provided onthe inlet circumference of the female die used in a first die forgingprocess has a larger angle than that provided on the inlet circumferenceof the female die used in a second die forging process.

Thus, a frictional resistance between the annular workpiece and thefemale die can be further reduced and the useful life span of the femaledie can be further extended.

Further, according to the process for manufacturing the drive plate, thehole is shaped into an oval, a star, or a cross. Thus, a material flowoccurring in a pressing operation enables a more secure pressingoperation. Further, even if a vibration and an impact act on the driveplate, the annular workpiece and the disc plate remain securelyconnected and are not disconnected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a drive plate manufactured by themanufacturing process of the present invention.

FIG. 2 is a block diagram showing an outline of the process formanufacturing the drive plate.

FIG. 3 is a cross sectional view outlining an annular workpiece, a fixeddie, and a female die in a first die forging process.

FIG. 4 is a cross sectional view outlining the annular workpiece, thefixed die, and the female die in a second die forging process.

FIG. 5 is a cross sectional view outlining the annular workpiece, aninner punch, and the female die in a trimming process.

FIG. 6 is a cross sectional view outlining an annular gear, a die, and acaulking punch in a pressing and a straightening process.

FIG. 7 shows shapes of holes as examples.

DESCRIPTION OF PREFERRED EMBODIMENT

Referring to the attached drawings, a process for manufacturing a driveplate according to the present invention is hereinafter described.

FIG. 1 is a cross sectional view of a drive plate 1 manufactured by themanufacturing process of the present invention.

FIG. 2 is a block diagram showing an outline of the manufacturingprocess. As illustrated in FIG. 2, the manufacturing process comprises afirst die forging process 101, a second die forging process 102, atrimming process 103, and a pressing and straightening process 104.

In the first die forging process 101, a die forging operation isperformed on an annular workpiece 2 using a fixed die 11 and a femaledie 12 as illustrated in FIG. 3. The female die 12 has a tooth profile13 formed on an inner circumference surface thereof. Further, the femaledie 12 has a chamfer 14 provided on an inlet inner circumference edgethereof, the chamfer 14 having an angle of 70°. A fine polishingoperation is performed on an upper outer circumference of the fixed die11 and an upper portion of the tooth profile 13 of the female die 12which slide on the annular workpiece 2. In the first die forging process101, the annular workpiece 2 is pressed into the female die 12 toapproximately 50% of the thickness thereof, so that a toothed part 3 isformed on an outer circumference of the annular workpiece 2 and eight totwelve bosses 4 are formed on an inner circumference thereof. The toothprofile 3 has an arc-shaped surface 15 formed at an end thereof by thechamfer 14 of the female die 12.

Next, the second die forging process 102 is performed on the annularworkpiece 2 manufactured through the first die forging process 101,using a fixed die 21 and a female die 22 as illustrated in FIG. 4. Thefemale die 22 has a tooth profile 23 formed on an inner circumferencesurface thereof, the tooth profile 23 having a depth of approximately70% of a thickness of the annular workpiece 2.

Further, the female die 22 has a chamfer 24 formed on an inlet innercircumference edge thereof, the chamfer 24 having an angle of 90°.

A fine finishing operation is performed on an upper outer circumferenceof the fixed die 21 and an upper portion of the tooth profile 23 whichslide on the annular workpiece 2.

At a bottom of the tooth profile 23 of the female die 22 a projection 25is formed to chamfer the toothed part 3 formed on the annular workpiece2. In the fixed die 21 concavities 26 are formed to produce eight totwelve projections from the bosses 4 formed in the annular workpiece 2.In the second die forging process 102, a chamfered tooth profile 3a isformed on the outer circumference of the annular workpiece 2 and eightto twelve projections 4a are formed on the inner circumference thereof,while an excess thickness 6 occurs on the outer circumference of theannular workpiece 2 and an excess thickness 7 occurs on the innercircumference thereof.

Next, the trimming process 103 is performed to trim some of the excessthickness 6 and 7 which are not needed for pressing the projections 4a,using an inner punch 31 and a female die 32 as shown in FIG. 5. At thesame time, while chipping the side of the toothed part 3a minutely, theexcess thickness 6 is trimmed to fabricate an annular gear 41. A toothedpart 42 undergoes a high frequency quenching operation. After thetrimming operation 103 is completed, the pressing and the straighteningprocess 104 is performed. Before performing the pressing andstraightening process 104, the orientation of the annnular gear 41 isreversed top to bottom, the toothed part 42 is fitted into toothed part44 formed on an inner circumference of a male die 43, the projections 4aof the annular gear 41 are inserted into holes 46 provided in a discplate 45, and a center guide pin 47 is inserted into a center hole 48. Apunch 49 crushes the projections 4a so that the disc plate 45 issecurely fixed on an inner circumference of the annular gear 41. Thus, adrive plate 1 is manufactured. In the high-frequency quenchingoperation, a deformation generated in the toothed part 42 of the annulargear 41 is eliminated.

During the pressing process, the projections 4a are crushed so that amaterial flow occurs in the hole 46. According to the present invention,the hole 46 is shaped into an oval, a star, a cross, or the like, sothat the excess thickness of the projections 4a spread over the hole 46,which leads to a more secure caulking operation. Thus, even if vibrationand impact act on the drive plate 1, the annular gear 41 and the discplate 45 remain securely connected and are not disconnnected.

To secure the ring gear 41 to the disc plate 45, a rivet can also beused.

The appropriate angle of the chamfer 14 is determined in the range of20°-150° according to the materials and the thickness of the annularworkpiece 2.

(INDUSTRIAL AVAILABILITY)

According to the manufacturing process, the existing press machine canbe used to manufacture the drive plate. Further, the principal parts,such as a female die and a punch, can be exchanged, so that many kindsof drive plates can be manufactured in a small amount. Also, therespective manufacturing process can be automated.

I claim:
 1. A process for manufacturing a drive plate, said processcomprising:subjecting an annular workpiece to a die forging using afemale die to form tooth profiles on an outer circumference of theannular workpiece and projections on an inner circumference thereof, thefemale die having a 20°-150° conical chamfer and a fine polished surfacefor sliding on the annular workpiece; trimming the annular workpiece;inserting the projections into holes on a disc plate so that the discplate is securely provided on an inner circumference of the annularworkpiece; and thereafter pressing the projections with a punch, wherebythe disc plate is securely fixed to the annular workpiece.
 2. Theprocess according to claim 1, wherein the die forging process consistsof two processes and the chamfer provided on the inner circumference ofthe female die used in the first die forging has a larger angle thanthat provided on an inner circumference of a female die used in thesecond die forging process.
 3. The process according to claim 1 or 2,wherein each of the holes is shaped into one of an oval, a star, and across.